Exploring thermal-hydraulic trade-offs in alternative FHR designs

Prismatic block type Fluoride-salt-cooled High temperature Reactors (FHRs) can benefit from Advanced Gas-cooled Reactor (AGRs) technologies. This paper contributes to the global FHR technology development by investigating achievable performance domain of an AGR-like FHR concept. Following recent design trade-off studies on this reactor concept using traditional pin-type ceramic fuel and annular internally cooled fuel, this paper further expands the FHR design space search by considering Fully Ceramic Microencapsulated (FCM) fuel in solid pellet, annular pellet and plate type fuel elements. Operating domain and maximum achievable power under safety constraints are identified for the considered fuel assembly designs. More design constraints have been included in this work in addition to those from previous study to ensure more practical reactor design. It has been found that for a pressure drop constrained core design, the fuel geometries considered in this study can potentially achieve up to a factor of 6.9 improvement in the core power density in comparison to a generic AGR while keeping the core operating parameters within the established safety limits.